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authorPeter Bengtsson <mail@peterbe.com>2020-12-08 14:43:23 -0500
committerPeter Bengtsson <mail@peterbe.com>2020-12-08 14:43:23 -0500
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+---
+title: Array.isArray()
+slug: Web/JavaScript/Reference/Global_Objects/Array/isArray
+tags:
+ - Array
+ - ECMAScript5
+ - JavaScript
+ - Method
+ - Reference
+ - polyfill
+ - 方法
+ - 陣列
+translation_of: Web/JavaScript/Reference/Global_Objects/Array/isArray
+---
+<div>{{JSRef}}</div>
+
+<p><code><strong>Array.isArray()</strong></code> 函式會檢查傳入的值是否為一個 {{jsxref("Array")}}。</p>
+
+<pre class="brush: js">Array.isArray([1, 2, 3]); // true
+Array.isArray({foo: 123}); // false
+Array.isArray('foobar'); // false
+Array.isArray(undefined); // false
+</pre>
+
+<h2 id="Syntax" name="Syntax">語法</h2>
+
+<pre class="syntaxbox">Array.isArray(<var>obj</var>)</pre>
+
+<h3 id="Parameters" name="Parameters">參數</h3>
+
+<dl>
+ <dt><code>obj</code></dt>
+ <dd>要檢查的物件。</dd>
+</dl>
+
+<h3 id="回傳值">回傳值</h3>
+
+<p>若物件為 {{jsxref("Array")}} 回傳 <code>true</code>;否則回傳 <code>false</code>。</p>
+
+<h2 id="Description" name="Description">描述</h2>
+
+<p>檢查傳入的物件是否為陣列({{jsxref("Array")}}),如果是便回傳 <code>true</code>,否則回傳 <code>false</code>。</p>
+
+<p>更多細節請參考 <a href="http://web.mit.edu/jwalden/www/isArray.html">“Determining with absolute accuracy whether or not a JavaScript object is an array”</a>。</p>
+
+<h2 id="Examples" name="Examples">範例</h2>
+
+<pre class="brush: js">// 下方都回傳 true
+Array.isArray([]);
+Array.isArray([1]);
+Array.isArray(new Array());
+Array.isArray(new Array('a', 'b', 'c', 'd'));
+Array.isArray(new Array(3));
+// 小細節:Array.prototype 本身是陣列:
+Array.isArray(Array.prototype);
+
+// 下方都回傳 false
+Array.isArray();
+Array.isArray({});
+Array.isArray(null);
+Array.isArray(undefined);
+Array.isArray(17);
+Array.isArray('Array');
+Array.isArray(true);
+Array.isArray(false);
+Array.isArray({ __proto__: Array.prototype });
+</pre>
+
+<h3 id="instanceof_vs_isArray"><code>instanceof</code> vs <code>isArray</code></h3>
+
+<p>當檢查 <code>Array</code> 實例時,<code>Array.isArray</code> 相較於 <code>instanceof</code> 更加推薦,因為它可以穿透 <code>iframes</code>。</p>
+
+<pre class="brush: js">var iframe = document.createElement('iframe');
+document.body.appendChild(iframe);
+xArray = window.frames[window.frames.length-1].Array;
+var arr = new xArray(1,2,3); // [1,2,3]
+
+// 正確地檢查陣列型態
+Array.isArray(arr); // true
+// 有害地,因為它不能在 iframes 之間正常運作
+arr instanceof Array; // false
+</pre>
+
+<h2 id="Polyfill">Polyfill</h2>
+
+<p>如果 <code>Array.isArray()</code> 不存在於您的環境,在其他程式碼前執行下列程式碼可建置 <code>Array.isArray()</code>。</p>
+
+<pre class="brush: js">if (!Array.isArray) {
+ Array.isArray = function(arg) {
+ return Object.prototype.toString.call(arg) === '[object Array]';
+ };
+}
+</pre>
+
+<h2 id="Specifications" name="Specifications">規範</h2>
+
+<table class="standard-table">
+ <tbody>
+ <tr>
+ <th scope="col">Specification</th>
+ <th scope="col">Status</th>
+ <th scope="col">Comment</th>
+ </tr>
+ <tr>
+ <td>{{SpecName('ES5.1', '#sec-15.4.3.2', 'Array.isArray')}}</td>
+ <td>{{Spec2('ES5.1')}}</td>
+ <td>Initial definition. Implemented in JavaScript 1.8.5.</td>
+ </tr>
+ <tr>
+ <td>{{SpecName('ES6', '#sec-array.isarray', 'Array.isArray')}}</td>
+ <td>{{Spec2('ES6')}}</td>
+ <td> </td>
+ </tr>
+ <tr>
+ <td>{{SpecName('ESDraft', '#sec-array.isarray', 'Array.isArray')}}</td>
+ <td>{{Spec2('ESDraft')}}</td>
+ <td> </td>
+ </tr>
+ </tbody>
+</table>
+
+<h2 id="Browser_compatibility" name="Browser_compatibility">瀏覽器相容性</h2>
+
+<div>
+
+
+<p>{{Compat("javascript.builtins.Array.isArray")}}</p>
+</div>
+
+<h2 id="See_also" name="See_also">參見</h2>
+
+<ul>
+ <li>{{jsxref("Array")}}</li>
+</ul>